How many calories should we feed our acute care patients? It is the biggest question we face when we are assessing what we are going to feed. There are many equations we can use, but the gold standard is, of course, Indirect Calorimetry. Our hospital, of course, does not have this equipment, so we carry on using our best judgement. This post will narrow in on total calorie recommendations and not protein.
There are many things that affect how much we can or should feed. How long has the patient been acutely ill, ie; what day of acute illness are we in? What is the medical stability of the patient, are they unstable and on pressor support? Has the patient been resuscitated adequately? What metabolic issues are apparent and could affect our decision, such as glucose levels. And, of course. what is their BMI.
When I have questions or I am stumped, I always refer to the Critical Care Guidelines for Estimating Energy Needs. I actually carry it with me in my notebook and refer to it often, sometimes weekly. As a matter of fact, I usually review estimated calorie needs daily with my acutely ill patients because their needs and their statuses can change dramatically over the course of a week or a few days.
For estimating calories for a BMI <30, you can use weight-based equations of 25-30 calories per kilogram.
For BMI 30-50, use 11-14 calories/kg of actual body weight. (ex. 160 kg X 11 cals = 1760 calories
BMI >50, 22-25 calories/kg of Ideal Body Weight. (ex. 200 kg with IBW of 78 kg X 22 cals = 1716 calories)
You can also use the Penn State Equation 2003b, which you will need to know the patients’ temperature and minute ventilation. This is the most accurate way to estimate metabolic rate in critical care patients.
When I have a critically ill patient, I use the calories per kilogram and the Penn State equation and evaluate how far apart they are. Generally, they are not very far apart. The Penn State is generally lower than the cals/kg and I generally use the Penn State equation for feeding during the first week of acute care illness.
Above is an example of the Penn State Equation, you can access it on-line from this website. mydietmanual.com
Where I work, we use the EMR called “Epic”. We have been able to integrate many of the equations we would normally use, such as: Kcals/kg, Mifflin St. Joer, Harris-Benedict (yes, I still look at this sometimes) , Penn State equation and modified Penn State Equation into our flow sheets so we can see what the differences are and use our best judgement when we are assessing needs.
Of course, I cannot discuss total calorie needs without mentioning propofol. This anesthetic is used often times for patients who are on a ventilator. The amount of calories it provides can vary from a small amount to a considerable amount. There are times that a patient may receive up to 800 or 1000 calories per day from propofol, so if this is not taken into account, patients can be easily over fed.
Propofol contains 1.1 calories per milliliter, but often times, nurses express the dose in how much per kilogram they are receiving. When assessing how much propofol a patient is receiving, you should always look at the pump to assess the volume the patient would be receiving that 24 hours. It may vary somewhat throughout the day, but usually not widely unless the patient is going to be extubated soon or if diprivan is being weaned so as to use another medication such as Midazolam (Versed).
Example= Propofol (Diprivan) infusing at 23 ml/hr: 23 X 24 hours = 552. 552 X 1.1 cal/ml = 607 calories per day from Propofol. This is a significant amount of calories, so the enteral formula you are using will most likely need to be a low calorie per ml formula that is very high in protein to prevent overfeeding and to meet protein goals. If the patient is being fed parenterally, then they do not need any lipids added because they are getting them from the propofol.
Another thing to consider is when to feed when a patient is on vasopressors (norepinephrine, dopamine, phenylephrine, epinephrine, vasopressin, dopamine). If a patient is stable, resuscitated and lactate is normal or falling rapidly, then feeding can usually start when doses of pressors (norepinephrine) are decreasing or stable, a goal is generally <.1-.3 µg/kg/min. Below is a link where you can access more information on this.
Critical Care Medicine 48(1):p 122-125, January 2020. | DOI: 10.1097/CCM.0000000000003965
During the initial ICU phase, consider a gradual progression of feeding so your target is met by day 4 of critical illness. Many times, it may take this long to reach a goal consistently though out the day as feedings are interrupted due to intolerance, nursing care, procedures and testing. You may not get to start feeding until almost day 2, but by day 4, they should be to goal.
I hope this is helpful!!!!
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